Mobile communication system, radio terminal used therefor, radio network controller and operation control method therefor

ABSTRACT

It is an object of the present invention to make it possible to grasp the number of terminals, which are planned to receive data of an MBMS service, accurately in an RNC even if movement of a radio terminal between RNCs occurs. In the case in which the movement of the radio terminal between RNCs has occurred during a period until the radio terminal actually received service data after it joined the MBMS service, the radio terminal notifies a moving destination RNC of at least identification information for specifying a moving source RNC. Then, the moving destination RNC notifies the RNC specified by the notified identification information that the radio terminal has left a cell. Consequently, both the moving source RNC and the moving destination RNC become capable of accurately grasping the number of radio terminals, which receive the service, and can perform judgment on whether a PtP system or a PtM system is adopted.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a mobile communication system, aradio terminal used therefor, a radio network controller and anoperation control method therefor. In particular, the present inventionrelates to a mobile communication system, which has a function forbroadcasting or multicasting service data including large volumecontents such as voices and images to a plurality of radio terminals(users), and a radio terminal used therefor, as well as a radio networkcontroller and an operation control method therefor.

[0003] 2. Description of the Prior Art

[0004] In a mobile communication system, there is a service forbroadcasting or multicasting large volume data of program contents to aplurality of radio terminals. This service is called an MBMS (MultimediaBroadcast Multicast Service). A schematic block diagram for such an MBMSfunction is shown in FIG. 5. Referring to FIG. 5, a BMSC (BroadcastMulticast Service Center) 1 is connected to an IP (internet Protocol)network 30 and is also connected to a plurality of RNCs (Radio NetworkControllers) 4 and 5 via a GGSN (Gateway GPRS (General Packet Service)Support Node) 2 and an SGSN (Serving GPRS Support Node) 3.

[0005] The RNC 4 has NodeBs (radio base stations) 6 and 7 under itscontrol and the RNC 5 has a NodeB 8 under its control. The respectiveNodeBs 6 to 8 are adapted to cover one or more cells 9 to 11, which areservice areas. In the figure, for simplification of explanation, eachNodeB is shown to cover one cell. Reference numeral 20 denotes a UE(user equipment), which indicates a radio terminal.

[0006] Note that interfaces between the SGSN 3 and the RNCs 4 and 5 arereferred to as Iu, and interfaces between the RNCs 4 and 5 and theNodeBs 6 to 8 are referred to as Iub. Moreover, Iur also exists as aninterface between the RNCs 4 and 5.

[0007] In the case in which the UE 20 shown in FIG. 5 desires delivery(broadcast/multicast) of the above-described MBMS service data,procedures shown in FIG. 6 are executed between the UE 20 and the BMSC1. In other words, “SUBSCRIPTION” for application for subscribership inthe service is generated by the UE 20 and sent to the BMSC 1 through theRNC 4 (step SI). Then, “SERVICE ANNOUNCEMENT” for announcement of theservice is sent from the BMSC 1 (step S2), and “JOINING” for requestingto join the service is sent from the UE 20 in response to “SERVICEANNOUNCEMENT” (step S3). Then, “MBMS MULTICAST MODE BEARER SET UP”,which is bearer setup for the MBMS, is applied to the RNC 4 by the BMSC1 (step S4).

[0008] Then, “MBMS NOTIFICATION” for notifying of the MBMS is sent fromthe RNC 4 to the UE 20 (step S5), and data of the MBMS is sent from theBMSC 1 to the RNC 4 (step S6). Thereafter, the data is delivered to theUE 20 (step S7). When delivery of all data ends, “MBMS MULTICAST MODEBEARER RELEASE” for bearer release is sent from the BMSC 1 (step S8),and “LEAVING” indicating withdrawal from the service is sent from the UE20 (step S9) to end the processing.

[0009] Such a procedure shown in FIG. 6 is only an outline. Details ofthe procedure are disclosed in the recommendation of the 3GPP

[0010] (Third Generation Partnership Project).

[0011] In such an MBMS, the RNC transfers service data to each UE in thecell under its control by the PtP (Point to Point) system or the PtM(Point to Multipoint) system. It is decided according to the number ofUEs, which are existing in the cell and joining to be planned to receivethe service data, whether the PtP system or the PtM system is used (seethe above-described document). In other words, when the number of UEshas reached a fixed value (threshold value) or more, in terms of savingtransmission power, the RNC delivers the service data by the PtM system.Conversely, when the number of UEs has fallen below the threshold value,the RNC delivers the service data by the PtP system.

[0012] After the UE has joined the service of the MBMS (step S3 of FIG.6), there is a short time until the UE actually becomes capable ofreceiving the service data (step S7). During the time, movement of theUE between RNCs may occur. In other words, in FIG. 5, it is possiblethat the UE 20 joins the service of the MBMS while it is in a zone ofthe cell 10 of the NodeB 7 under the control of the RNC 4, and beforereceiving the service data, moves to the cell 11 of the NodeB 8 underthe control of the RNC 5.

[0013] In such a case, the UE 20 notifies a moving destination RNC 5that it has moved to the cell 11 under the control of the movingdestination RNC 5. Thus, the moving destination RNC 5 is capable oflearning that the UE 20 has moved thereto. However, in the currentsystem, the moving source RNC 4 has no means for learning that the UE 20has left the cell 10 under its control.

[0014] As described above, in the RNC, in delivering the service data ofthe MBMS, it is decided according to the number of UEs, which areplanned to receive the service data, whether the PtP system or the PtMsystem is used. Thus, the RNC is required to grasp the number of UEs.However, the moving source RNC cannot learn the number of UEs.

BRIEF SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide a mobilecommunication system, which is capable of grasping the number of UEs,which are planned to receive data of an MBMS service accurately even ifmovement of a UE between RNCs occurs, and a radio terminal usedtherefor, as well as a radio network controller and an operation controlmethod therefor.

[0016] A mobile communication system according to the present inventionis a mobile communication system having a function for delivering dataof an identical service to a plurality of radio terminals, which ischaracterized in that, in accordance with movement of a radio terminalhaving joined the service between radio network controllers, themovement of the radio terminal is notified from a moving destinationradio network controller to a moving source radio network controller.

[0017] A radio network controller according to the present invention isa radio network controller in a mobile communication system having afunction for delivering data of an identical service to a plurality ofradio terminals, which is characterized by including means which, when aradio terminal having joined the service has moved to a cell undercontrol of the radio network controller, notifies a moving source radionetwork controller of the movement of the radio terminal.

[0018] A operation control method according to the present invention isan operation control method for a radio network controller in a mobilecommunication system having a function for delivering data of anidentical service to a plurality of radio terminals, which ischaracterized by including a step of, when a radio terminal havingjoined the service has moved to a cell under control of the radionetwork controller, notifying a moving source radio network controllerof the movement of the radio terminal.

[0019] A radio terminal according to the present invention is a radioterminal in a mobile communication system having a function fordelivering data of an identical service to a plurality of users, whichis characterized by including means which, in response to movement ofthe radio terminal between radio network controllers after the radioterminal has joined the service, sends identification informationspecifying a moving source radio network controller to a movingdestination radio network controller.

[0020] A program according to the present invention is a program forcausing a computer to execute an operation control method for a radionetwork controller in a mobile communication system having a functionfor delivering data of an identical service to a plurality of radioterminals, which is characterized by including a step of, when a radioterminal having joined the service has moved to a cell under control ofthe radio network controller, notifying a moving source radio networkcontroller of the movement of the radio terminal.

[0021] Operations of the present invention will be described. In amobile communication system having an MBMS function for delivering MBMSservice data (identical data) including large volume contents such asvoices or images to a plurality of radio terminals, in the case in whichmovement of a radio terminal between radio network controllers hasoccurred during a period until the radio terminal actually receivedservice data after it joined the service, at least identificationinformation for specifying a moving source radio network controller isnotified from the radio terminal to a moving destination radio networkcontroller. Then, the moving destination radio network controllernotifies the radio network controller specified by the notifiedidentification information that the radio terminal has left a cell.

[0022] Consequently, not only the moving source radio network controllerbut also the moving destination radio network controller can accuratelygrasp the number of radio terminals, which receive the service, and thedetermination on whether the PtP system or the PtM system is used can beperformed accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the accompanying drawings:

[0024]FIG. 1 is a functional block diagram of an RNC (radio networkcontroller) which is applied to an embodiment of the present invention;

[0025]FIG. 2 is an operation sequence diagram of a first embodiment ofthe present invention;

[0026]FIG. 3 is an operation sequence diagram of a second embodiment ofthe present invention;

[0027]FIG. 4 is an operation sequence diagram of a third embodiment ofthe present invention;

[0028]FIG. 5 is a schematic diagram of a mobile communication system towhich the present invention is applied; and

[0029]FIG. 6 is an operation sequence diagram of an MBMS service.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Embodiments of the present invention will be hereinafterdescribed with reference to the accompanying drawings. FIG. 1 is aschematic functional block diagram of an RNC (radio network controller)in the embodiments of the present invention. It is assumed that the RNCis a moving destination RNC 5 in the case in which a UE 20 moves betweenRNCs in the system diagram of FIG. 5. Referring to FIG. 1, anotification unit 40 for notifying a message to a UE (radio terminal)moving source has a function for, following the movement of the UE 20between the RNCs shown in FIG. 5, notifying a moving source RNC that theUE 20 has left the cell 10 on the basis of a signal sent from the UE. AUE number counting unit 41 has a function for counting the number of UEswhich exist in a zone of a cell under control of the RNC and receive anidentical service.

[0031] A PtP/PtM judgment unit 42 has a function for judging whether adelivery system for MBMS service data is set to a PtP system or a PtMsystem according to a counting value of the UE number counting unit 41.An RB setting unit 43 has a function for performing bearer setup fordelivery of the MBMS service data in accordance with the judgment in thePtP/PtM judgment unit 42. A communication unit 44 has a function forcommunicating with the NodeB under its control and with the BMSC 1 viathe upper SGSN3 and GGSN 2 and also communicating with the other RNC (4)via the interface Iur between the RNCs.

[0032] A control unit 45 is a CPU (central processing unit: computer). Amemory 46 has a ROM having stored therein an operation procedure for theCPU as a program in advance and a RAM serving as a work memory for theCPU. Control of the respective units 40 to 44 is executed by this CPU inaccordance with the program. Note that reference numeral 47 denotes acommon bus.

[0033]FIG. 2 is a sequence diagram showing an operation procedure of afirst embodiment of the present invention. The sequence diagram shows anoperation sequence among the UE 20, the moving destination RNC 5, andthe moving source RNC 4 shown in FIG. 5. As a premise in thisembodiment, it is assumed that the UE 20 has moved from the cell 10under control of the RNC 4 to the cell 11 under control of the RNC 5during a period until the UE 20 could actually receive service dataafter it joined the MBMS service (an idle mode or a standby state), andthat a radio bearer for the MBMS has not been set in the movingdestination cell 11 and no radio bearer has been set in the UE 20.

[0034] When the UE 20 has moved from the cell 10 to the cell 11according to the movement of the UE 20 between RNCs, it sends a messageof “MBMS Mobility Update”, to the moving destination RNC 5 (step Sll).It is assumed that this message includes an “MBMS Service ID” forspecifying the MBMS service, a “UE ID” for specifying the UE 20, and an“RNC ID” for specifying the moving source RNC. The RNC 5 having receivedthis notification counts up the number of UEs, which receive the MBMSservice, by “1” with the UE number counting unit 41 (step S12).

[0035] At the same time, the RNC 5 sends a message, which notifies thatthe UE 20 has left a cell, to the moving source RNC 4 via the Iurinterface with the notification unit 40 for notifying a message to a UEmoving source (step S13). It is assumed that this message includes an“MBMS Service ID” for specifying the MBMS service and a “UE ID” forspecifying the UE 20. The RNC 4 having received this notification countsdown the number of UEs, which receive the MBMS service, by “1” with theUE number counting unit 41 (step S14). The moving destination RNC 5sends “MBMS Mobility Update Confirm”, which is a massage forconfirmation, to the UE 20 (step S15). This message includes an “MBMSservice ID” and a “UE ID”.

[0036]FIG. 3 is a sequence diagram showing an operation procedure of asecond embodiment of the present invention. FIG. 3 shows an operationsequence among the UE 20, the moving destination RNC 5, and the movingsource RNC 4 shown in FIG. 5. As a premise in this embodiment, it isassumed that the UE 20 has moved from the cell 10 under control of theRNC 4 to the cell 11 under control of the RNC 5 during a period untilthe UE 20 could actually receive service data after it joined the MBMSservice (an idle mode or a standby state), and that data of the MBMSservice has already been transmitted to the moving destination cell 11by the PtM system.

[0037] In this embodiment, steps S11 to S15 of the sequence areidentical with those in FIG. 2 in the first embodiment. Thereafter, amessage for setup of an RB (radio bearer) for the MBMS service is sentto the UE 20 from the RNC 5 (step S16). This message includes an “MBMSService ID” and an “MBMS RB parameter”. The “MBMS RB parameter” isinformation indicating a channel of the radio bearer. Consequently, theUE 20 can make connection to a common channel, through which the MBMSservice data is delivered, to receive the service.

[0038]FIG. 4 is a sequence diagram showing an operation procedure of athird embodiment of the present invention. FIG. 4 shows an operationsequence among the UE 20, the moving destination RNC 5, and the movingsource RNC 4 shown in FIG. 5. As a premise in this embodiment, it isassumed that the UE 20 has moved from the cell 10 under control of theRNC 4 to the cell 11 under control of the RNC 5 during a period untilthe UE 20 could actually receive service data after it joined the MBMSservice (an idle mode or a standby state), and that data of the MBMSservice has already been transmitted to the moving destination cell 11according to the PtP system.

[0039] In this embodiment, steps S11 to S15 of the sequence areidentical with those in FIG. 2 in the first embodiment. Thereafter,judgment on the PtP system and the PtM system is performed in thePtP/PtM judgment unit 42 in the RNC 5. Since this judgment depends uponthe number of UEs, the number of UEs (a counted value of the UE numbercounting unit 41) and a threshold value are compared. If the number ofUEs is smaller than the threshold value (“Y” in step S17), the PtPsystem is maintained, and service data is delivered through a dedicatedchannel for each UE. Therefore, an “RB Setup” message is also sent tothe UE 20 from the RB setting unit 43 of the RNC 5 such that the data isdelivered by the PtP system (step S18). This message includes aparameter indicating a channel of the radio bearer.

[0040] If it is judged in step S17 that the number of UEs is equal to ormore than the threshold value, the PtP system is switched to the PtMsystem in the RB setting unit 43 (step S19), and a message for setup ofthe RB (radio bearer) for the MBMS service is sent to the UE 20 (stepS20). This message includes an “MBMS Service ID”, a “UE ID”, and an“MBMS RB parameter”. The “MBMS RB parameter” is information indicating achannel of the radio bearer. Consequently, the UE 20 can make connectionto a common channel, through which the MBMS service data is delivered,to receive the service. The massage (step 20) which indicates that thePtP dedicated channel is switched to the PtM common channel, is alsosent to other UEs which receive the same service.

[0041] As described above, according to the present invention, both themoving source RNC and the moving destination RNC become capable oflearning that a UE has left a cell or entered a zone of the cell. Thus,there is an effect that switching of the PtP system and the PtM systemwith respect to a radio bearer for delivery of MBMS service data can beperformed appropriately.

What is claimed is:
 1. A mobile communication system having a functionfor delivering data of an identical service to a plurality of radioterminals, wherein, in accordance with movement of a radio terminalhaving joined the service between radio network controllers, themovement of said radio terminal is notified from a moving destinationradio network controller to a moving source radio network controller. 2.The mobile communication system according to claim 1, wherein themovement of the radio terminal between radio network controllers ismovement during a period until data reception after said radio terminalhas joined the service.
 3. The mobile communication system accordingclaim 2, wherein said movement of the radio terminal is movement duringan idle mode or a standby state.
 4. The mobile communication systemaccording to claim 1, wherein said moving source radio networkcontroller reduces to update the number of radio terminals subscribingto the service in response to the notification.
 5. The mobilecommunication system according to claim 1, wherein said movingdestination radio network controller increases to update the number ofradio terminals subscribing to the service.
 6. The mobile communicationsystem according to claim 5, wherein said moving destination radionetwork controller has already set up a common channel for delivery ofdata of the service, and sets the common channel with respect to saidradio terminal moving between radio network controllers.
 7. The mobilecommunication system according to claim 5, wherein said movingdestination radio network controller has already set a dedicated channelfor data delivery of the service with respect to radio terminals havingjoined the service and, in accordance with the updated number of saidradio terminals, judges that the dedicated channel be switched to thecommon channel for the data delivery of the service.
 8. The mobilecommunication system according to claim 5, wherein, in the judgment,said moving destination radio network controller compares the updatednumber and a predetermined number and, if the updated number is smallerthan the predetermined number, sets the dedicated channel with respectto said radio terminal moving between radio network controllers.
 9. Themobile communication system according to claim 5, wherein, in thejudgment, said moving destination radio network controller compares theupdated number and a predetermined number and, if the updated number isequal to or larger than the predetermined number, sets the commonchannel with respect to said radio terminals having joined the serviceand said radio terminal moving between radio network controllers.
 10. Aradio network controller having a function for delivering data of anidentical service to a plurality of radio terminals, comprising meansfor, when a radio terminal having joined the service has moved to a cellunder control of the radio network controller, notifying a moving sourceradio network controller of the movement of said radio terminal.
 11. Theradio network controller according to claim 10, wherein the movement ofsaid radio terminal to the cell is movement during a period until datareception after said radio terminal has joined the service. 12 The radionetwork controller according to claim 11, wherein said movement of theradio terminal is movement during an idle mode or a standby state. 13.The radio network controller according to claim 10, further comprisingmeans for increasing and updating the number of radio terminalssubscribing to the service.
 14. The radio network controller accordingto claim 13, the radio network controller having already set up a commonchannel for delivery of data of the service, further comprising meansfor setting the common channel with respect to said radio terminalhaving moved to the cell.
 15. The radio network controller according toclaim 13, wherein said radio network controller further comprises meansfor, when the radio network controller has already set a dedicatedchannel for data delivery of the service with respect to radio terminalshaving joined the service, in accordance with the updated number of saidradio terminals, judging that the dedicated channel be switched to thecommon channel for the data delivery of the service.
 16. The radionetwork controller according to claim 15, wherein, in the judgment, saidradio network controller compares the updated number and a predeterminednumber and, if the updated number is smaller than the predeterminednumber, sets the dedicated channel with respect to said radio terminalhaving moved to the cell.
 17. The radio network controller according toclaim 15, wherein, in the judgment, said radio network controllercompares the updated number and a predetermined number and, if theupdated number is equal to or larger than the predetermined number, setsthe common channel with respect to said radio terminals having joinedthe service and said radio terminal having moved to the cell.
 18. Aoperation control method for a radio network controller in a mobilecommunication system having a function for delivering data of anidentical service to a plurality of radio terminals, comprising a stepof, when a radio terminal having joined the service has moved to a cellunder control of said radio network controller, notifying a movingsource radio network controller of the movement of said radio terminal.19. The operation control method according to claim 18, wherein themovement of said radio terminal to the cell is movement during a perioduntil data reception after said radio terminal has joined the service.20. The operation control method according to claim 19, wherein saidmovement of the radio terminal is movement during an idle mode orstandby state.
 21. The operation control method according to claim 18,further comprising a step of increasing and updating the number of radioterminals subscribing to the service.
 22. The operation control methodaccording to claim 21, the operation control method having already setup a common channel for delivery of data of the service, furthercomprising a step of setting the common channel with respect to saidradio terminal having moved to the cell.
 23. The operation controlmethod according to claim 21, the operation control method havingalready set a dedicated channel for data delivery of the service withrespect to radio terminals having joined the service, further comprisinga step of, in accordance with the updated number of said radioterminals, judging that the dedicated channel be switched to the commonchannel for the data delivery of the service.
 24. The operation controlmethod according to claim 23, wherein, in the judgment, said operationcontrol method compares the updated number and a predetermined numberand, if the updated number is smaller than the predetermined number,sets the dedicated channel with respect to said radio terminal havingmoved to the cell.
 25. The operation control method according to claim23, wherein, in the judgment, said operation control method compares theupdated number and a predetermined number and, if the updated number isequal to or larger than the predetermined number, sets the commonchannel with respect to said radio terminals having joined the serviceand said radio terminal having moved to the cell.
 26. A radio terminalin a mobile communication system having a function for delivering dataof an identical service to a plurality of users, comprising means for,in response to movement of said radio terminal between radio networkcontrollers after said radio terminal has joined the service,transmitting identification information specifying a moving source radionetwork controller to a moving destination radio network controller. 27.A computer readable program for causing a computer to execute anoperation control method for a radio network controller in a mobilecommunication system having a function for delivering data of anidentical service to a plurality of radio terminals, comprising a stepof, when a radio terminal having joined the service has moved to a cellunder control of said radio network controller, notifying a movingsource radio network controller of the movement of said radio terminal.